It is not a grand piece of engineering. At its narrowest, the section crossing the lake is only about a metre wide, a single file of dumped stone, meaning it was built by tipping and packing rubble rather than by any more refined method. What makes it quietly odd is what happens once it reaches the island: the path continues for a further 41 metres across land, but it does so in a zig-zag pattern, as though deliberately avoiding something, or threading between features that no longer survive. It ends at a gap in a stone wall.

The full causeway stretches 78 metres in total, with the lake-crossing portion accounting for 37 metres and the land portion the remaining 41. Its purpose was presumably to give reliable access to Church Island, a category of island found across Ireland that typically held a small ecclesiastical site, often a church or burial ground serving the surrounding community. The causeway's dump construction is an ancient and practical technique common to Irish lake crossings, related in spirit to the crannóg tradition, in which artificial or modified islands were linked to the shore by similar stone or timber paths. A section of the causeway has been widened in more recent times, reaching 3.2 metres across, but the original narrower outline, at 1.1 metres wide, remains clearly visible alongside it.

The causeway is accessible from the north-eastern shore of Lough Carra, where the island lies close enough to the mainland that the crossing, though short, would once have been impassable without it. The zig-zag section on the island is worth following to its conclusion at the wall opening, since it suggests the island's layout was once more structured than it may now appear.